The present invention relates to an low-staining agent for aqueous paint to be used especially for surface finishing treatment of various materials, such as metal, glass, porcelain tile, concrete, siding board, extrusion-molded plate, plastics, and the like, which are used outside, and further to a low-staining aqueous paint composition to which the low-staining agent is added. The low-staining agent for aqueous paint of the present invention and the aqueous paint composition using the same are paints that are used especially for surface coating of a structure such as an architecture or a bridge, and may be a paint directly applied on a base material or can be used as a paint for final finishing paint such as various finishing paints, patterning paints, stony surface paints, and pattern paints.
Recently, in the field of paints to be used for architectures and civil-engineered structures, a transition from solvent-type paints using organic solvent to aqueous paints using water as a solvent is taking place. This is carried out for the purposes of reducing the damage to health of paint workers and inhabitants and of reducing the ambient air pollution, and the aqueous paints for use are increasing in number year by year.
Some of the known aqueous paints have the same level of efficiency with the solvent-type paints concerning the weather resistance and the water resistance. However, with respect to the staining resistance property in particular, aqueous paints advertised as a low-staining type is at present far from the level of the solvent-type low-staining paints.
Also, the coating film by the aqueous paint generally has a lower coating film hardness as compared with the coating film by a organic solvent based paint, and the penetration of an adhering staining substance tends to be high. Therefore, once a staining substance adheres, it is often difficult to remove the stain from the coating film surface.
As a low-staining paint that has solved such a problem, WO 94/06870 discloses an art of blending a specific organosilicate and/or its condensation product into a paint. More specifically, the art disclosed in WO 94/06870 is characterized in that a specific organosilicate and/or its condensation product is blended, and the coating film surface is made hydrophilic by treating the coating film with an acid after the coating film formation, so that an oily staining substance will not adhere easily and the adhering staining substance will be washed away together with water drops of falling rain, for example.
However, in the art disclosed in WO 94/06870, an organosilicate and/or its condensation product is simply added to an organic solvent paint. A paint obtained by adding an organosilicate and/or its condensation product to the aqueous paint by applying this prior art to an aqueous paint has the following problems because of poor compatibility between the aqueous paint and the organosilicate and/or its condensation product, and these problems must be solved for its practical application
1) In many cases, sediments are generated in the mixture in a short time after the addition (within about one hour)
2) An aqueous clear paint that does not contain any pigment forms a turbid coating film.
3) In an aqueous paint having a high luster and generally referred to as xe2x80x9cgloss paintxe2x80x9d, its surface luster considerably decreases.
These seem to be due to the poor compatibility between the aqueous paint and the organosilicate and/or its condensation product as mentioned above.
The problems to be solved by the present invention are as follows.
a. To provide a low-staining agent that can outstandingly improve the anti-staining, property and the property of preventing penetration of the staining substance when it is added to an aqueous paint.
b. To provide a low-staining agent that does not affect the weather resistance and the water resistance and that does not affect the luster when it is added to an aqueous paint.
c. To provide a low-staining agent excellent in the compatibility with an aqueous paint.
Also, the purpose of the present invention is to provide a low-staining aqueous paint composition to which said low-staining agent is added.
The inventors of the present invention have made an eager study in order to solve these problems and found out that a good coating film having a good anti-staining property and a resistance to penetration of a staining substance, and further being excellent in weather resistance and water resistance can be formed by adding a modified condensation product of alkoxysilane having at least one polyalkylene oxide group to various aqueous paints, thereby completing the present invention.
The present invention relates to the following aqueous paint low-staining agent and an aqueous paint composition using the same.
The invention described in claim 1 relates to an aqueous paint low-staining agent characterized by being a modified condensation product of alkoxysilane having at least one polyoxyalkylene group and an alkoxyl group, wherein a repetition unit of said polyoxyalkylene group has 1 to 4 carbon atoms, and said alkoxyl group has 1 to 4 carbon atoms.
The invention described in claim 2 relates to an aqueous paint low-staining agent according to claim 1, characterized in that said polyoxyalkylene group is a polyoxyethylene group having two carbon atoms in the repetition unit , and said alkoxyl group is an ethoxy group having two carbon atoms.
The invention described in claim 3 relates to a low-staining aqueous paint composition characterized in that 1.0 to 40.0 parts by weight, as converted in terms of SiO2, of an aqueous paint low-staining agent (B) are added to 100 parts by weight of a solid component of a synthetic resin emulsion (A), said aqueous paint low-staining agent being a modified condensation product of alkoxysilane having it least one polyoxyalkylene group and an alkoxyl group, wherein a repetition unit of said polyoxyalkylene group has 1 to 4 carbon atoms, and said alkoxyl group has 1 to 4 carbon atoms.
In the above-mentioned low-staining aqueous paint composition, it is preferable that said aqueous paint low-staining agent (B) is one in which said polyoxyalkylene group is a polyoxyethylene group having two carbon atoms in the repetition unit, and said alkoxyl group is an ethoxy group having two carbon atoms.
It is preferable that the synthetic resin emulsion (A) to be used in the low-staining aqueous paint composition of the present invention is one selected from an acrylic resin emulsion, an acrylic silicone resin emulsion, a fluorine containing resin emulsion, and an polyurethane resin emulsion; and it is especially suitable that these synthetic resin emulsions are cross-linkable type emulsions.
The invention described in claim 10 relates to a process for use of a low-staining aqueous paint composition, characterized in that 1.0 to 40.0 parts by weight, as converted in terms of SiO2, of an aqueous paint low-staining agent (B) are added and mixed to 100 parts by weight of a solid component of a synthetic resin emulsion (A) for painting, said aqueous paint low-staining agent being a modified condensation product of alkoxysilane having at least one polyoxyalkylene group and an alkoxyl group, wherein a repetition unit of said polyoxyalkylene group has 1 to 4 carbon atoms, and said alkoxyl group has 1 to 4 carbon atoms.
The low-staining agent reacts with water, so that one should avoid keeping it in contact with a water-containing synthetic resin emulsion for an excessively long period of time. The above construction enables the low-staining aqueous paint composition to sufficiently exhibit its inherent characteristics by using it in the distribution stage as a multi-component type paint having two or more components and mixing them at the time of use.